Asthma Treatment Response Modified by PM2.5, NO2, and O3 Among African American Children: A Reanalysis of the AsthmaNet's BARD Trial.
Background: Asthma morbidity significantly affects children of all racial backgrounds; however, African American children experience a greater disease burden than children from other racial groups. Despite the known influence of air pollution on asthma outcomes, its role in the efficacy of asthma treatments remains underexplored.
Objective: To examine how exposure to particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) influenced treatment outcomes in the NIH AsthmaNet Best African American Response to Asthma Drugs (BARD) trial.
Methods: The BARD trial randomized 224 African American children to four asthma treatments consisting of inhaled corticosteroids (ICS) and long-acting beta antagonists (LABA) administered in a randomized crossover fashion. Treatment efficacy was assessed by the frequency of asthma exacerbations, percent predicted FEV1 (%PFEV1), and annualized asthma control days. Residential exposures to PM2.5, NO2, and O3 were estimated using a validated spatiotemporal model. Mixed effects models were used to evaluate the interaction between pollution exposure and treatment efficacy, adjusting for age, household triggers and trial site.
Results: PM2.5, NO2, and O3 exposures ranged substantially across participants: from 2.28 - 15.3 μg/m3, 2.34 - 63.7 ppm, and 2.57 - 23.7 ppb, respectively. NO2 and PM2.5 exposures were not associated with increased exacerbations post-treatment (p for interaction = 0.15 and 0.08, respectively). However, NO2 exposure significantly modified the effect of high-dose ICS+LABA therapy on lung function. Children with below median NO2 exposures while on ICS + LABA had a reduction of 5.86 (1.16, 10.56) in %PFEV1 compared to those with above-median NO2 exposures.
Conclusions: Residential high NO2 exposure may significantly attenuate the efficacy of ICS+LABA therapy on lung function in African American children. These findings suggest the need to consider environmental factors in clinical trials and asthma management strategies.